Electro-rheological fluids are slurries composed of a non-conducting fluid medium and a particulate. The particulate is responsive to a high-voltage electric field applied across small gap (1-2 mm) electrodes placed in the fluid. The reaction by the particulate effectively changes the viscosity of the fluid in the localized area between the electrodes.
The particulate typically consists of a carrier and an electro-rheological constituent which is responsive to the applied electric field. In order for the effective change in viscosity to remain uniform over time, it is necessary to keep the particulate in suspension within the fluid. However, prior art particulates have been limited in the amount of electro-rheological constituent that they can contain. This results in the use of relatively large particulate (on the order of 100 microns) being introduced into the non-conducting fluid medium. Large particulate require continuous mixing in order to keep the particulate uniformly suspended in the fluid. In addition, large particulate may cause various fluid filters to clog during the use of the electro-rheological fluid.